<div class="doc-item" id="doc-1427"><h2 class="doc-item-name">underive<span class="namespace">(clojure.core)</span></h2><ul class="var-arglists"><li>(<span class="var-name">underive</span> tag parent)</li><li>(<span class="var-name">underive</span> h tag parent)</li></ul><div class="var-docstring"><p>Removes a parent/child relationship between parent and
  tag. h must be a hierarchy obtained from make-hierarchy, if not
  supplied defaults to, and modifies, the global hierarchy.</p></div><div class="var-source"><pre>; clojure/core.clj:3372
(defn underive
  ([tag parent] (alter-var-root #'global-hierarchy underive tag parent) nil)
  ([h tag parent]
   (let [tp (:parents h)
         td (:descendants h)
         ta (:ancestors h)
         tf (fn [m source sources target targets]
              (reduce
               (fn [ret k]
                 (assoc ret k
                        (reduce disj (get targets k) (cons target (targets target)))))
               m (cons source (sources source))))]
     (if (contains? (tp tag) parent)
       {:parent (assoc (:parents h) tag (disj (get tp tag) parent))
        :ancestors (tf (:ancestors h) tag td parent ta)
        :descendants (tf (:descendants h) parent ta tag td)}
       h))))</pre></div><div class="license"><p>Copyright (c) Rich Hickey. All rights reserved.</p><p>The use and distribution terms for this software are covered by the <a href="http://opensource.org/licenses/eclipse-1.0.php">Eclipse Public License 1.0</a>, which can be found in the file
          epl-v10.html at the root of this distribution. By using this software
          in any fashion, you are agreeing to be bound by the terms of this
          license. You must not remove this notice, or any other, from this
          software.</p></div></div>